In recent years, heat-radiation reflective glass having a small visible light transmittance is used in glass for cars and vehicles or buildings so that they can be air-conditioned at a lower load and the hotness due to direct sunlight can be reduced. Such heat-radiation reflective glass having a small visible light transmittance is worth using also from the viewpoint of the protection of privacy. Heat-radiation reflective glass that can meet such needs is conventionally obtained by a method of forming a film on the glass surface by vacuum deposition or sputtering of a highly conductive material such as titanium nitride or silver. A method is also available in which an oxide film containing cobalt, iron, chromium or nickel is formed on a glass plate by thermal decomposition.
Of the above film forming methods, however, the method of forming a film by vacuum deposition or sputtering of a highly conductive material such as titanium nitride or silver has the problem of a high production cost. As for the method in which an oxide film is formed on a glass plate by thermal decomposition, the method can be simply operated and can enjoy a low production cost, but has the problem that, depending on the composition of oxide film, the glass with a film formed may cause a great change in transmittance, a deterioration of chemical resistance of the film or a clouding of the film, when subjected to tempering.